Radio Technique

IIOGeorgeMMyers SAY GEORGE whats difference be-its pins totally enclosed plastic tosized wire connect red probe tween positive negative pulses andavoid short circuitsbattery pack plug terminal bearing red better can tell what kind B red wire black wirewire black black Dont let RC system has what pulseconnected plug Sometimes therepins touch because will discharge used anyway about summarizeswill white wire too will disre-pack hurry things will get hot questions subject mostgard discussionThe meter should reading 5 s frequently asked C unused pin pin posi-This exercise verifies red wire begin neither better thetion plug pin carries con-connected positive battery voltage difference simply direction thetrol signal servo plugthe black negative battery uses electrons flowing control signal answer obvious question yessome other colors identify positive wire However cant mix positive- andyou can plug servo batterynegative wires way Cox/Sanwa negative-pulse servos using pulsepack plug causing damageinstance used black wires white inverter see May 1977 columntho cant see reason itstripe positive lead Lets perform simple test find out next demonstration will need Now its time remove voltmeter what kind pulse RC system usesa DC voltmeter scale 6 volts orconnections connect battery pack Take out flight battery pack lookmore sensitivity least 20000to flight system usual way Leave plug Note following Fig 1ohms per volt Connect red probe tothe switch turned off Insert voltshows typical plugthe plus V2A terminal blackmeter connections receiver plugs battery plug similar thewire minus common terminalreceptacles placing red lead posi plug servos except fact thatNow using pins bits appropriately-tive terminal black lead nega tive terminal another location make easier avoid short circuits Plug servo remaining receptacles ATTERYTurn receiver verify have made correct connections ob LUGserving voltmeter reads same value before Turn transmitter verify system operation making servo move Battery voltage may drop slightly servo moving Finally move black meter lead Ijone control-signal terminals system uses positive pulses meter should read about /4 volt less battery voltage system uses negative pulses meter should reading about /4 volt demonstration over turn everything off remove meter con nections NoteObserve determined pulse po thlarity input servos no cal Cpolarity consideration transmitted signal negative-pulse system trans mitter will work positive-pulse system flight pack perfectly long pulse configurations compatible servos will center themselves off center control functions may appear different servos throttle may control rudder etc Only decoder servos concerned pulse polarity thats important point have discoursed pulses point ever defining what speaking RC systems pulses bits control information originating transmitter response way Fig 1 Typical plugs showing corresponding locations f battery s s control pulses have set control sticks trims 14 Model Aviation switches encoder trans mitter interrogates control potenti ometer transmitter sequentially generates series On/Off commands radio-frequency oscillator transmitter time between Off signals control information may see television screen bright bar changes width move sticks Fig 3 may neces sary switch channel 2 4 re place TV antenna 36-in length wire see pattern dont want bore everyone long discussion control information moves fingertips airplane please accept statement On/ Off switching transmitter results change voltage servos control signal line voltage goes up transmitter down transmitter switches off Most radio systems use up time 2 3 milli seconds 002 003 seconds since control signal repeated about 30 times per second easy see control signal spends far time down up about 033 seconds down Up can either positive negative voltage pulse named accordingly Now its time critical question What type pulse does servo hand want receive Assuming wouldnt asking question matching decoder test Id like suggest servo tester such Ace R/C Inc Servo Cycle discussed last month dont have rest system cant refer battery pack clue proper plus minus voltage leads either thats important Connect servo backwards will blow out its lit tle electronic brain However cases red/black color code discussed earlier will answer question Connect plus minus voltage leads appropriate servo plug pins Temporarily connect signal pin either positive negative signal lead Turn Servo Cycle watch carefully servo runs end its travel stays turn off immedi ately Youve got about three seconds fore something will damaged servo amplifier Thats enough time test youre quick Grab servo arm twist back center can connect signal lead other control pulse Turn system servo should happily chugging back forth have system automatic Now know what kind pulse wants Mark case Well thats about electronics can stand spring Theres lot lovely flying weather outside Im gonna put use Write youve got problems ideas column George M Myers 70 Froehlich Farm Rd Hicksville NY 11801 ON \Qq/7 -3IXMTRI Li BATTER Servo Cycle Auto ON RCR BAVY BATY Low Volts tive PulseHigh Volts tive Pulse 1 TRY PULSE servo runs end stays thereDISCON NECTI 2 TRY THE OTHER PULSE Servo should cycle back forth Negative Pulse Y Positive Pulse Fig 4 Servo polarity test set-up POSITIVE PULSE SYSTEMSNEGATIVE PULSE SYSTEMS WORLD ENGINES EXPERT KRAFT ACE DIGITAL COMMANDER COX/SANWA H EAT H K IT PRO-LINE OS EK prior 1973 MRC Fig 5 Some pulse polarities measured operating receivers no guarantee product given manufacturer will use pulses described above August1977 15 Fig 2 Test set-up determining control pulse polarh nf tha rn-iuAr anndAr Fig 3 TV screen makes visible control signals transmitter pattern may roll up down pulse repetition rate exactly 30HZ thats acceptable